Multi-scale temporal-spatial variability of the East Asian summer monsoon frontal system: observation versus its representation in the GFDL HiRAM

Li, Yana; Deng, Yi; Yang, Song; Zhang, Henian; Ming, Yi; Shen, Zhencai

doi:10.1007/s00382-018-4546-z

Cited by 14 publications

(10 citation statements)

References 39 publications

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“…This sudden onset of poleward progression moves the front north of 35 • N over eastern China by the 1 st dekad of July. The pattern outlined, consisting of a quick northward progression of the EASM front in June-July following a period without noticeable meridional displacement during spring is in good agreement with the literature described in Section 1, seeLi et al (2019),Wang and LinHo (2002) andKong and Chiang (2020) among others.…”

supporting

confidence: 89%

“…The algorithm used to detect the EASM front in our analysis is adapted from Li et al (2018Li et al ( , 2019, and based on the meridional gradient of equivalent potential temperature (θ e hereafter). In Li et al (2019), points in the domain (22…”

Section: Frontal Detection Algorithmmentioning

confidence: 99%

“…The frontal detection algorithm described contains a more robust, albeit more convoluted, computation of the frontal band than in Li et al (2019). This allows the identification of the EASM front in every day of the chosen dataset, provided a front exists in the region and has a sufficient zonal extension to be associated with synoptic-scale (and larger) dynamics.…”

Section: Frontal Detection Algorithmmentioning

confidence: 99%

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The interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression

Volonté

Turner

Schiemann

et al. 2021

Preprint

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Abstract. The East Asian summer monsoon (EASM) is a complex phenomenon, influenced by both tropical and mid-latitude dynamics and by the presence of the Tibetan Plateau. The EASM front neatly separates tropical and extratropical air masses as the monsoon marches northwards. Although the different factors behind EASM progression are illustrated in a number of studies, their interactions, in particular between tropical and extratropical air masses, still need to be clarified. In this study we apply Eulerian and Lagrangian methods to the ERA5 reanalysis dataset to provide a comprehensive study of the seasonal evolution and variability of the EASM, and we highlight the dynamics of the air masses converging at its front. A frontal detection algorithm is used to perform a front-centred analysis of EASM evolution. The analysis highlights the primary role of the sub-tropical westerly jet (STWJ) in controlling the strength and the poleward progression of the EASM front, in particular during Mei Yu, one of the stages of EASM progression. The upper-level mid-latitude forcing acts in conjunction with the southerly advection of low-level moist tropical air, modulated by the seasonal cycle of the South Asian monsoon and by the location of the Western North Pacific subtropical high. The Mei Yu stage is distinguished by an especially clear interaction between tropical and mid-latitude air masses converging at the EASM front. The analysis of composites based on the latitude of the EASM front during Mei Yu reveals the influence of the STWJ on the strength of the mid-latitude flow impacting on the northern side of the EASM front. In turn, this affects the extent of the warm moist advection on its southern side and the distribution and intensity of resultant rainfall over China. This study shows the validity of an analysis of EASM evolution focused on its front and on the related low-level airstreams, at least in the Mei Yu stage. The framework highlighted shows how the upper-level flow drives the low-level airstreams that converge at the EASM front, thus controlling the shape of EASM progression. This framework provides a basis for studies of climate variability and extreme events and for model evaluation.

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supporting

confidence: 89%

Section: Frontal Detection Algorithmmentioning

confidence: 99%

Section: Frontal Detection Algorithmmentioning

confidence: 99%

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The interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression

Volonté

Turner

Schiemann

et al. 2021

Preprint

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“…5a,b). Because this rain belt primarily results from the interaction between the warm humid air from the south and the cold air from the north (Li et al 2019), its diabatic heating profile is shallower than that of the deep convection in the tropics. The differences in diabatic heating between NGTR and F2000 exhibit a dipole pattern (Figs.…”

Section: Mechanisms For Changes In Atmospheric Circulation and Precipitation A Circulation Diagnosis Via Geopotential Tendency Equationmentioning

confidence: 99%

Effects of Suppressed Transient Eddies by the Tibetan Plateau on the East Asian Summer Monsoon

et al. 2021

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It is known that the Tibetan Plateau (TP) can weaken the transient eddies (TEs) transported along the westerly jet stream. This study investigates the effects of the persistently suppressed TEs by the TP on the East Asian summer monsoon and the associated mechanisms using the NCAR Community Earth System Model. A nudging method is used to modify the suppression of the TEs without changing the steady dynamic and thermodynamic effects of the TP.The suppressed TEs by the TP weaken the East Asian westerly jet stream through the weakened poleward TE vorticity flux. On the one hand, the weakened jet stream leads to less (more) rainfall in northern (southern) East Asia by inducing anomalous moisture convergence, mid-tropospheric warm advection, and upper-level divergence, particularly in early summer when the eastward propagation of TE suppression by the TP is strong. On the other hand, the precipitation anomalies can shift the East Asian westerly jet stream southward and promote the moisture convergence in southern East Asia through latent heat release. Therefore, the persistent suppression of the TEs leads to a southward shift of the East Asian rain belt by a convective feedback, as previously found that the steady thermodynamic and dynamic forcings of the TP favored a northward shift of the rain belt. This study suggests that the anomalously weak TEs can lead to the south-more-north-less rainfall change over East Asia.

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“…Meanwhile, studies also pay much attention to the large‐scale physical processes and dynamics of the Asian monsoon, including coupled monsoon system and SST‐monsoon relationship (Webster, 2006), land‐monsoon interaction (Yasunari, 2006), and dynamical and thermal effects of the Tibetan Plateau (TP, Yanai & Wu, 2006). Evaluation of high‐resolution atmospheric model by Li et al (2018; Y. Li, et al, 2019) indicated that the multiscale temporal‐spatial variability of the East Asian Meiyu‐Baiu fronts is connected with the western North Pacific subtropical high in association with ocean‐land sea level pressure contrast over East Asia. Atmospheric heating over the Tibetan Plateau can enhance East Asian subtropical frontal rainfall through two distinct Rossby wave trains and the isentropic uplift to the east of the TP, which deforms the western Pacific subtropical high and enhances moisture convergence toward the East Asian subtropical front (Wang et al, 2009; Yanai & Wu, 2006).…”

Section: Introductionmentioning

confidence: 99%

Multiscale Variability of Meiyu and Its Prediction: A New Review

Ping²,

et al. 2020

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Following the description of the basic climatic characteristics of Meiyu in East Asia, we present a comprehensive review of multi–time scale variabilities of the Meiyu together with the long‐term change of extreme precipitation during the Meiyu in this paper. The dynamic prediction skills of the Meiyu on subseasonal to seasonal time scales are further described and illustrated by using present numerical prediction models. For the multi–time scale variabilities of the East Asian Meiyu, they are closely related with the impacts of both quasi‐biweekly and 30–60 day oscillation from both the tropics and the middle and high latitudes on intraseasonal time scale, the influences of El Niño–Southern Oscillation and the Tropospheric Biennial Oscillation on interannual time scale, the variations of East Asian summer monsoon on decadal time scale, and the continued impacts of global warming, Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation on interdecadal scale and long‐term trend. Under the background of the global warming and the influences of urbanization and aerosol effects, the Meiyu shows some specific characteristics including significantly weakened continuous rain, uneven spatial distribution of precipitation, and increased (decreased) number of strong (weak) precipitation days. Improvements of prediction on rain belt location, total precipitation amount, persistent heavy precipitation events, and low‐frequency variability oscillation during Meiyu season have been achieved with the improved dynamic models of the Beijing Climate Center since 2010.

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Multi-scale temporal-spatial variability of the East Asian summer monsoon frontal system: observation versus its representation in the GFDL HiRAM

Cited by 14 publications

References 39 publications

The interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression

The interaction of tropical and extratropical air masses controlling East Asian summer monsoon progression

Effects of Suppressed Transient Eddies by the Tibetan Plateau on the East Asian Summer Monsoon

Multiscale Variability of Meiyu and Its Prediction: A New Review

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